This invention relates generally to level-shifting circuitry.
As is known in the art, level-shifting circuitry is used to shift lower voltage signal levels to higher voltage signal levels. One example of such circuit is shown in FIG. 1. Such circuit 9 is formed on a semiconductor chip and includes a pair of N type Metal Oxide Semiconductor Field Effect Transistors (MOSEETS) N1 and N2 and a pair of P type MOSFETs P1 P2 arranged as shown. The P type MOSFETs have the bulk silicon connected to an external +2.5 volt power source. The N type MOSFETs have the bulk silicon connected to ground. The N type MOSFET N1 is a low threshold voltage transistor. The gate of transistor N1 is connected to an internal +2.1 volt source. The input voltage (IN) is a logic signal having logic 1, here represented by +2.1 volts or a logic 0 state, here represented by ground potential. Here, the level-shifter also provides an inversion in the logic state of the input signal as well as shifting the input signal logic 1 state from +2.1 volts to a higher voltage output signal logic 1 state, here +2.5 volts. Thus, in operation, when the input voltage is logic 0, transistors N1, and P2 are “on” and transistors P1 and N2 are “off”, thereby providing a logic 1, here a +2.5 volt level, at the output OUT. Thus, the input logic 1 condition of a +2.1 volt input signal has been shifted to a +2.5 volt output logic 1. On the other hand, when the input voltage IN is logic 1 (i.e., here +2.1 volts), transistors N1, and P2 are “off” and transistors P1 and N2 are “on”, thereby providing ground potential (i.e., an output logic 0) at the output OUT.